Beneficiation of ores



Feb. 27, 1962 J. F. HASEMAN 3,022,956

BENEFICIATION OF ORES Filed April 14, v1958 tion progresses.

Filed Apr. 14, 1958, Ser. No. 728,122 3 Claims. (Cl. 241--24) The present invention generally relates to the beneficiation of ores yand more particularly relates to a method for beneiciating magnetite-apatite ores such as those found in the Province of Ontario, Canada. The novel process of this invention is applicable for the benetciation of any magnetite-apatite ore in which the magnetic iron values may be substantially completely liberated from the normagnetic apatite values.

The phosphate industry requires, for the production of fertilizers, superphosphate and triple superphosphate, a phosphatic material of yrelatively high BPL (bone phosphate of lime) value and imposes penalties where impurities, such as iron compounds, alumina, etc., are present in excess of certain minimum fixed percentages.

Similarly, the iron industry requires for the production of pig iron, material of relatively high iron value, and the -material should also be low in impurities such as'phosphates.

In the Province of Ontario, Canada, in certain igenous rock formations, large deposits of magnetite-apatite ores occur. It is also believed that large deposits of such ores may be found in the igneous rock formations in the Rocky Mountains and Appalachian Mountains. y

Inorder to be attractive on a commercial scale, a process for beneciating a magnetite-apatite ore should, therefore, produce a magnetite concentrate which is relatively free of phosphate values and the process should also produce an apatite concentrate which is relatively free of iron values. The present invention is directed to providing such a process. v

An objectuof the'v present invention isv to provide a process for beneiiciating a magnetite-apatite ore.

A further object of the present invention is to provide a process for beneciating a magnetite-apatite ore, which Aprocess produces a m-agnetite concentrate which is relatively free of phosphate values and an apatite concentrate which is relatively free of iron values.

Another object of the invention is to provide a process for beneiciating a magnetite-apatite ore wherein magnetic methods of separation are employed to provide commercially attractive yields.

These and other objects and advantages of the present invention will be apparent as the description of the invenln accordance with the present invention, it has been ldiscovered that eminently satisfactory beneiiciation of magnetite-apatite ores and minerals can be achieved magnetically by a series of critical and interdependent process steps. The process of this invention does not require any high temperature heating or roasting of the ore as is required in some processes and yet provides commercially attractive yields of magnetite and apatite' concentrates.

Generally described, the present invention is a magnetic process for beneciating a magnetite-apatite ore which comprises subjecting the ore while in a state of subdivision suiiicient to liberate substantial amounts of magnetite from epatite to a low intensity magnetic Aseparation and separately recovering a first magnetic fracaired States Fatent O magnetic separation.

Mice

tion and a rst non-magnetic traction, and subjecting the magnetic fraction to a wet low intensity magnetic separation and separately recovering a second magnetic fraction and a second non-magnetic traction. Y

The mineral or ore processed in accordance with the invention must initially be subdivided to a degree requisite to liberate substantial amounts of the magnctite from the apatite. The exact particle size necessary to liberation will vary with the crystal size of the minerals. ln general, reduction in particle size to less than about 14 mesh is sulicient to liberate the magnetite from the apatite and to liberate these 'minerals from other gangue materials. Reduction to a particle size of less than about Z0() mesh generally provides a feed material which is too finely divided and dusty for commercial operation, IlFurther, it

has been found that very nely divided material is not particularly amenable to magnetic methods of separation. The ore is, therefore, preferably liberated in a manner so as to produce a minimum of finely divided material. The ore may be liberated to a degree sufficient to substantially completely liberate the magnetite from the apatite; however, when substantially complete liberation. is performed, substantial amounts of -200 mesh particles are produced which, as above set forth, is not desirable. In the preferred method of operation, the ore is liberated to a degree sufiicient to etect at least liberation and more preferably to eliect at least liberation but less than 95% liberation. The ore may be comminuted in any conventional apparatus of the art, including, without limitation, grinders, Ajaw Crushers, cone crushers, roll Crushers, hammer mills, ball mills and the like. The specific apparatus used should be selected and operated with 'the'production of a minimum amount of fines kept in consideration.

The comminuted ore is subjected to a magnetic separation'at a relatively low intensity of magnetism, This magnetic separation may be either a wet magnetic separation or a dry magnetic separation; however, for economic reasons, which will hereinafter be apparent, a dry magnetic separation is preferred for this step of the process.

The low intensity magnetic separation produces an attracted portion or first magnetic concentrate and an 'unattracted portion or first non-magnetic concentrate.

The first magnetic concentrate or magnetite rougher concentrate contains the larger proportion of the magnetite values inthe ore feed and contains a substantially smaller proportion o-f the apatite values. Similarly, the first nonmagnetic fraction or apatite rougher concentrate contains the larger proportion of the apatite values and the smaller proportion of the magnetite values.

I magnetic separation is still of the low intensity type.

As hereinbefore set forth, the ore feed to the process may be comminuted to effect substantially complete liberation of the magnetite from the apatite, but preferably the ore is comminuted to a lesser degree. When the ore is comminuted to a lesser degree, for example to liberation of the components, the lirst magnetic fraction recovered from the low intensity magnetic separation is preferably comminuted to effect substantially complete `liberation of the mineral constituents in the fraction before subjecting it to the wet low intensity This com-minution may be per formed dry or Wet; however, since the subsequent low intensity magnetic separation is a wet separation, and since wet comminution has produced the best results with a minimum production of fines of n200 mesh, a Wet comminution is preferred. As in the rst comminution operation, any suitable apparatus may be used for this comminution step of the process.

The comminuted ore is then subjected to the wet low intensity magnetic separation. In the event that the second comminution is performed dry, water must be added to the comminuted ore. This second low intensity separation is preferably a wet separation since experimental results have indicated that a wetcseparation will produce a magnetic concentrate which meets the specifications set by the iron industry. Speciiically, it is necessary that the phosphate content in the iron concentrate be very low and a wet magnetic separation will produce such a concentrate.

The wet low intensity magnetic separation is conducted so as to produce at least two fractions; namely, an attracted portion which is a magnetic fraction (the magnetite concentrate of the process) and an unattracted portion which is a non-magnetic fraction. This non-magnetic fraction is high in apatite values and may be recovered as a product of the process but it is preferably further proccssed, as is hereinafter set forth in detail.

Brielly summarizing the description so far set forth, a comminuted epatite ore is subjected to a low. intensity magnetic separation to produce a rst magnetic fraction and a rst non-magnetic fraction, the rst magnetic fraction is subjected to a wet magnetic separation to produce a second magnetic fraction which is the magnetite. concentrate of the process and a second non-magnetic.

fraction.

The initial low intensity magnetic separation produced a first magnetic fraction, whichV was Vfurthertreated as hereinbefore described, and a first non-magnetic fraction.

This non-magnetic fraction is relatively high in epatite.V values, but it also contains magnetite values. The nonmagnetic fraction is, therefore, subjected to a dry high intensity magnetic separation. In order to be an effective high intensity magnetic separation, the operation must be conducted dry. When the initial low intensity magnetic separation is a dry separation, the non-magnetic fraction obtained may be passed directly to the high intensity magnetic separation step of the process. However, when the initial low intensity separation is performed wet,` the nonmagnetic fraction is obtained wet and it is necessary yto dry this fraction before conducting the high intensity separation on this fraction.

ln any event, the dry ordried non-magnetic fraction is subjected to a high intensity magnetic separation to produce an attracted, magnetic fraction and an unattracted or non-magnetic fraction. rlhis non-magnetic fraction is high in apatite and low in magnetite and is recovered as the apatite concentrate of the process. The magnetic fraction is lower in apatite and higher in magnetite and may be sent to waste or further processed to recover one or more of the components.

The non-magnetic fraction recovered from the wet low intensity magnetic separation step of the process may be dried and combined with the apatite concentrate re` covered from the high intensity magnetic separation step of the process to produce a combined epatite concentrate of the process. This non-magnetic fraction from thc wet low intensity magnetic separation step, however, has some magnetite values mixed with the epatite and it is preferable to subject this fraction to a high intensity magnetic separation. A preferred manner of accomplishing this is to dry this fraction and introduce it to the high intensity magnetic separation step along with the non-magnetic fraction recovered from the initial low intensity magnetic separation step. I-hese two non-magnetic fractions may be admixcd before introduction to the high intensity step or may be separately introduced.

A Vmore Yspecific and detailed description of the invention will be given with reference to the accompanying drawing which is a flow sheet illustrating the general application of the process of the invention. This drawing is intended merely as one illustration and not as a limitation of the invention. Modifications of the process illustrated by this flow sheet, while employing the principles of the instant invention, will be apparent to those familiar with magnetic separation processes in general.

Referring to the drawing, magnetitefapatite ore 11, as mined, is subjected to a crushing process at 13 to substantially liberate the magnetite values from the apatite values. The crushing operation produces a predominantly -14 +200 mesh feed which is subjected to a dry low intensity magnetic separation at 15. The dry low intensity magnetic separation at 15 produces the attracted fraction or magnetite rougher concentrate 17 and the unattracted, non-magnetic fraction 19.

The initial lowV intensity magnetic separation may be a wet separation; this alternate operation is indicated by the dotted line leading from the crusher 13 to the wet low intensity magnetic separation zone 21. The magnetite rougher concentrate 23 as obtained in this wet separation may be passed to a grinding zone 25 as indicated by the dotted line. The nonmagnetic fraction 2.7 from the wet separation, however, is thickened in a thickener A2) .and dried in a drier 31before subjecting it to the high intensity magnetic separation at 33. Y

VThe masnetite rougher concentrate 17 and/or 23 is introduced to the grinding zone 25 in which the concenvtrate is comrninuted to effect substantially complete liberation of the magnetite from the epatite. If the crushing at 13 was of a degree to liberate substantially all of the magnette from the epatite, the grinding at 25 may be eliminated and the magnetic rougher concentrate 17 and/or 23 may be passed directly to a Wet low intensity magnetic separation zone 35 as indicated by the dotted line 38,.

The magnetite rougher concentrate 17 and/or 23, with or without further comminution at V25, is subjected to the wet low intensity magnetic separation 35 and a magnetite concentrate 37 and a non-magnetic fraction 39 are produced. The non-magnetic fraction 39 is thickened at 41 and dried at 43. If the dried non-magnetic fraction at 43 is found to be of low enough magnetite content, it may be directly recovered as the epatite concentrate 45 as indicated by the dotted line 47. However, it is preferred to upgrade this fraction in the high ntensity magnetic separation z one 33.

In any event, -the fraction o r fractions from zones 43 and/or 19 and/or 31 are introduced into the high intensity magnetic separation zone 33 in a dry state; As a result ofthe high intensity magnetic separation 33, a non-magnetic fraction 45, the apatite concentrate of the process, is produced and a magnetic'fraction 49 is also produced. The magnetic fraction 49 mayl be recycled to the process or otherwise treated to recover the magnetite and apatite values therefrom.

The following example is given to illustrate specific applications of the instant novel process and is not to be construed as limiting the invention thereto.

Example A magnetite-apatite ore mined from a deposit in the vicinity of Nemegos, Ontario, Canada, was subjected to -a mineralogical examination. The'analysis indicated that the ore had the following composition:

A sample of the ore was crushed to -35 mesh and an analysis indicated that at -35 mesh 85% of the magnetite was liberated from the apatite. had the following size analysis.

This crushed ore Screen size: Weight- Percent The crushed ore sample was subjected to a low intensity magnetic separation. 74% of the feed was recovered as a magnetic fraction and 26% was recovered as a non-magnetic fraction. Analysis of the magnetic an non-magnetic fractions are given below. v

Magnetic: Percent Fe203 90.5 P205 0.6

Non-magnetic:

The magnetic fraction was wet ground in a rod mill until 95% would pass through a 48 mesh screen. This ground wet material was subjected to -a low intensity wet magnetic separation. A magnetic concentrate and a non-magnetic fraction were recovered. The magnetic magnetite concentrate was 72.8% by weight of the original ore sample and represented a 97% recovery of magnetite values. The magnetic magnetite concentrate analyzed Percent F6203 TiOz 8.6 P205 0.13 S 0.01

It may be noted that the phosphate content in this concentrate was very low which illustrates the eflicient separation of magnetite from apatite.

The non-magnetic fraction obtained from this wet separation represented 1.2% of the original ore sample and was combined with the non-magnetic fraction obtained from the initial low intensity magnetic separa-tion. The combined non-magnetic fraction which represented 27.2% by weight of the original ore was then subjected to a high intensity magnetic separation and a magnetic fraction and a non-magnetic fraction were separately recovered. The magnetic fraction represented 3.3% by Weight of the original ore sample and was analyzed as being 35% apatite and 30% magnetite. This fraction was not processed further.

The non-magnetic fraction was recovered as the apatite concentrate of the process. It was 23.9% by weight of the original ore sample and represented a 94% recovery of apatite. The concentrate was analyzed as:

This illustrates the eicient separation of apatite from magnetite.

The description of the invention utilized specic reference to certain process details; however, it is to be understood that such details are illustrative only and not :by way of limitation. Other modifications and equivalents of the invention will be apparent to those skilled in the art from the foregoing description.

Having now fully described and illustrated the invention, what is desired to be secured and claimed by Let ters Patent is set forth in the -appended claims.

l. A process for beneficiation of a magnetite-apatite ore which comprises comminuting the ore to at least 70% liberation but less than 95 liberation of magnetite from apatite, subjecting the comminuted ore to a dry low intensity magnetic separation and separately recovering a first magnetic fraction containing the larger proportion of the magnetic values and a first non-magnetic fraction containing the larger proportion of the apatite Values, subjecting the first magnetic fraction to a comminu-ting operation to elfect substantially complete liberation of magnetite from apatite, subsequently subjecting the comminuted magnetic fraction to a wet low intensity magnetic separation and separately recovering a second magnetic fraction of low lapatite content and a second nonmagnetic fraction.

2. A process for beneiciation of a magnetite-apatite ore which comprises subjecting the ore while in a state of subdivision suicient to liberate substantial amounts of magnetite from apatite to a dry low intensity magnetic separation and separately recovering a lirst magnetic fraction containing the larger proportion of the magnetic values and a first non-magnetic fraction containing the larger proportion of the apatite values, subjecting the magnetic fraction to a wet low intensity magnetic separation and separately recovering a second magnetic fraction of low apatite content and a second non-magnetic fraction, drying said second non-magnetic fraction and subjecting said first non-magnetic fraction and the dried second non-magnetic fraction to a high intensity magnetic separation and separately recovering a -magnetic fraction tand a non-magnetic fraction of low magnetite content.

3. A process for beneciation of a magnetite-apatite ore which comprises comminuting the ore to at least 70% liberation but less than 95% liberation of magnetite from apatite, subjecting the comminuted ore to a dry low intensity magnetic separation and separately recovering a rst magnetic fraction containing the larger proportion of the magnetic values and a first non-magnetic fraction containing the larger proportion of the apatite values, subjecting the iirst magnetic fraction to a cornminuting operation to effect substantially complete libera- .tion of magnetite from apatite, subsequently subjecting the comminuted magnetic fraction to a wet low intensity magnetic separation and separately recovering a second magnetic fraction of low apatite content and a second non-magnetic fraction, drying said second non-magnetic fraction and subjecting said first non-magnetic fraction and the dried second non-magnetic fraction to a high intensity magnetic separation and separately recovering a magnetic fraction and a non-magnetic fraction of low magnetite content.

References Cited in the file of this patent UNITED STATES PATENTS Conkling Aug. 29, 1893 Edison July 8, 1902 Le Baron et al Feb. 19, 1952 OTHER REFERENCES Taggart: Handbook of Mineral Dressing, 1947, sec. 13, page 32.

Bureau of Mines, Report of Investigations No. 3980, December 1946. 

1. A PROCESS FOR BENEFICIATION OF A MAGNETITE-APATITE ORE WHICH COMPRISES COMMINUTING THE ORE TO AT LEAST 70% LIBERATION BUT LESS THAN 95% LIBERATION OF MAGNETITE FROM APATITE, SUBJECTING THE COMMINUTED ORE TO A DRY LOW INTENSITY MAGNETIC SEPARATION AND SEPARATELY RECOVERING A FIRST MAGNETIC FRACTION CONTAINING THE LARGER PROPORTION OF THE MAGNETIC VALUES AND A FIRST NON-MAGNETIC FRACTION CONTAINING THE LARGER PROPORTION OF THE APATITE VALUES, SUBJECTING THE FIRST MAGNETIC FRACTION TO A COMMINUTING OPERATION TO EFFECT SUBSTANTIALLY COMPLETE LIBERATION OF MAGNETITE FROM APATITE, SUBSEQUENTLY SUBJECTING THE COMMINUTED MAGNETIC FRACTION TO A WET LOW INTENSITY MAGNETIC SEPARATION AND SEPARATELY RECOVERING A SECOND MAGNETIC FRACTION OF LOW APATITE CONTENT AND A SECOND NONMAGNETIC FRACTION. 